Figure 5.

Location of the MPTA common core. A–C, Maximal cross-sectional area of effective (solid pink) and noneffective (hatched blue) microinjections are collected onto a single rostrocaudal plane (−8.8 mm). The track of the injection pipette in these trials actually lay over the range of −8.0 to −9.16 mm caudal to bregma. A, Dye spread for the 17 small effective muscimol microinjections largely overlap (10 or 20 nL, 9 rats, 10 on the left and 7 on the right). The region in common to all (intersection), on the right and on the left, is shown in solid red (dark). The term “common core” refers to this area on the right. Noneffective microinjections (10–200 nL) surround the effective ones (14 microinjections in 12 rats). B, As in A, but showing areas of both large and small effective muscimol microinjections (24 left, 11 right in 23 rats). Noneffective trials are not shown. The solid red area on the right is common to all 11 microinjections on that side. The (smaller) solid red area on the left is common to 22 of the 24 left-sided microinjections. Dye spread areas of the two microinjections not included fell closely nearby (black outlines, rats #322 and #15, 50 and 200 nL, respectively). C, Dye spread areas of 10 saline (control) microinjections (5 rats; 50–200 nL; horizontal dark blue lines) overlapped the common core zone bilaterally (5 left, 5 right). None of these yielded a significant bonus time.